Strategies for Improved 3D Small-Tip Fast Recovery Imaging
Strategies for Improved 3D Small-Tip Fast Recovery Imaging
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DOI：
10.1002/mrm.24947
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发表时间：
2014-08-01
影响因子：
3.3
通讯作者：
Nielsen, Jon-Fredrik
中科院分区：
文献类型：
--
作者：
Sun, Hao;Fessler, Jeffrey A.;Nielsen, Jon-Fredrik
目的：小尖端快速恢复（STFR）成像是最近提出的稳态序列，具有与平衡稳态自由进动相似的图像对比度，但具有同时去除条带伪影和瞬态波动的潜力。STFR依赖于在自由进动（数据采集）间隔期间针对累积相位定制的“向上翻转”射频（RF）脉冲，其被设计为使自旋回到纵向轴线，从而在下一个脉冲重复时间内将横向磁化保持为纵向磁化。我们最近提出了一种适用于薄板成像的射频扰频STFR序列，然而，在许多应用中，例如。例如，在一个实施例中，功能磁共振成像或各向同性分辨率结构成像，三维（3D）稳态成像是理想的。不幸的是，由于需要3D定制的RF脉冲，3D STFR成像具有挑战性。在这里，我们提出了新的战略，为改善三维STFR成像，基于（i）未受污染的成像，和（ii）联合设计的nonslice-selective tip-down/tip-up RF pulses.Theory和Methods：我们推导出一个分析信号模型的建议未受污染的STFR序列，并提出了两种策略，用于设计的3D定制tip-down/tip-up RF脉冲。我们验证的分析结果，使用幻影和在体内imaging experiments.Results：我们的分析模型和成像实验表明，建议的未受污染的STFR序列是不太敏感的提示激励错误相比，相应的破坏序列，因此，可能是一个有吸引力的候选人的三维成像。建议的“联合”RF脉冲设计方法，其中我们制定的tip-down/tip-up RF脉冲设计任务作为一个幅度最小二乘问题，产生适度的改进，一个更简单的“分离”的设计方法。使用建议的未受破坏的序列和联合RF脉冲设计，我们证明了平衡的稳态自由旋进样信号特性，但减少banding.Conclusion：使用建议的未受破坏的序列和联合RF脉冲设计，STFR脑图像在一个三维区域的利益与平衡的稳态自由旋进样信号特性，但减少了条带的原理证明3D STFR脑图像可以得到。(C)2013 Wiley Periodicals，Inc.
Purpose: Small-tip fast recovery (STFR) imaging is a recently proposed steady-state sequence that has similar image contrast as balanced steady-state free precession but has the potential to simultaneously remove banding artifacts and transient fluctuation. STFR relies on a "tip-up" radiofrequency (RF) pulse tailored to the accumulated phase during the free precession (data acquisition) interval, designed to bring spins back to the longitudinal axis, thereby preserving transverse magnetization as longitudinal magnetization for the next pulse repetition time. We recently proposed an RF-spoiled STFR sequence suitable for thin slab imaging, however, in many applications, e. g., functional magnetic resonance imaging or isotropic-resolution structural imaging, three-dimensional (3D) steady-state imaging is desirable. Unfortunately, 3D STFR imaging is challenging due to the need for 3D tailored RF pulses. Here, we propose new strategies for improved 3D STFR imaging, based on (i) unspoiled imaging, and (ii) joint design of nonslice-selective tip-down/tip-up RF pulses.Theory and Methods: We derive an analytic signal model for the proposed unspoiled STFR sequence, and propose two strategies for designing the 3D tailored tip-down/tip-up RF pulses. We validate the analytic results using phantom and in vivo imaging experiments.Results: Our analytic model and imaging experiments demonstrate that the proposed unspoiled STFR sequence is less sensitive to tip-up excitation error compared to the corresponding spoiled sequence, and may, therefore, be an attractive candidate for 3D imaging. The proposed "joint" RF pulse design method, in which we formulate the tip-down/tip-up RF pulse design task as a magnitude least squares problem, produces modest improvement over a simpler "Separate" design approach. Using the proposed unspoiled sequence and joint RF pulse design, we demonstrate proof-of-principle 3D STFR brain images with balanced steady-state free precession-like signal properties but with reduced banding.Conclusion: Using the proposed unspoiled sequence and joint RF pulse design, STFR brain images in a 3D region of interest with balanced steady-state free precession-like signal properties but with reduced banding can be obtained. (C) 2013 Wiley Periodicals, Inc.